Rex tried it again inside the inner world at a spot where the flame wouldn't want to try and kill him. During his frequent fights with the flame, he had to most of the time dodge and ran away from it but he discovered that when he got a distance away from it, it wouldn't try to catch him.
Whether the flame felt that he was just an ant and didn't intend to catch him when he was at this far or whether it was something else, it didn't matter for him. This was a place where he could test and train and so he trained. At first, it was like trying to hold water with his hands his mental energy would slip away the moment he tried. He tried and tried again till he would be kicked out of that inner world due to his mental energy being drained. But gradually, his efforts bore fruit.
He learned how to shape his willpower into various shapes, the only limiter was his imagination plus mental strength and capacity. He would train till he thought he could beat the lame before challenging it. It was train, battle, train....battle continuously. With each battle, his mental strength grew stronger as well as his control over it. Though he still couldn't do much damage to the flame, the duration of the battles became longer.
Finally, after what felt like months of gruelling effort, Rex stood in his inner world, battered, his body had burn marks here and there, his entire shirt had been burnt but he himself remained unyielding.
Rex stood in the vast expanse of his inner world, sweat dripping from his brow. Before him danced the dark flame, his own element that was also his enemy in this battle. It formed tendrils which squirmed and twisted, their fiery ends snapping like whips, eager to strike.
He had lost count of how many times he had faced against this dark flame. The battles were a blur of pain and exhaustion, each time he got killed in this mental world and go out into the real world. But what he had gotten from them were experience, fighting experience. The flame lashed out, a blazing tendril whipping toward him with blistering speed.
Rex sidestepped, his movements fluid. Unlike his first few battles, when he had barely managed to stumble out of the way, his reflexes now felt sharp, his body honed by countless hours of training. The tendril missed him by a hair's breadth, searing the air where he had been moments before.
Another tendril came from his left, this one faster and more unpredictable. Rex ducked low, spinning on his heel as the flame whipped past him. The sensation of heat grazed his skin, but he remained unscathed.
Gripping his mental spear tightly, he lunged forward, meeting the next tendril head-on. The collision sent a resounding pang echoing through the inner world, as if steel had struck steel. The flame recoiled, its tendril curling back like a wounded serpent.
Rex didn't let this chance slip up. He advanced with ferocity, thrusting his spear at the flame's core. Each clash of his weapon against the fiery tendrils sent vibrations through his arms, but he held firm.
Throughout the battles he had faced with the weapons he had used, he liked the spear the most and was the reason for his usage. Being able to use it with this much proficiency, without a teacher was quite the talent. Unlike children of his age who should just be learning how to hold their elements, Rex was facing a battle. It wasn't to say that he didn't had the teacher, his enemy was his own teacher and the battles were a learning experience for him.
The flame surged, its tendrils lashing out in a chaotic flurry, a last ditch effort to overwhelm him. But Rex was ready. He moved like a shadow, weaving through the barrage parrying from time to time.
"This ends now....."
Finally, with a defiant roar, he thrust his spear forward, piercing through a particularly thick tendril and driving the flame backward. The entity recoiled, its movements faltering as it struggled to maintain its form.
Rex saw his opening and pressed his advantage. With a series of rapid strikes, he forced the flame to the ground. It flickered weakly, it had no more power nor energy whereas Rex still had some to spare.
He stood over it, his spear poised to deliver the final blow. The flame was at his mercy, its once mighty presence now reduced to a feeble glow beneath his feet. Pointing his spear at the flame, time seemed to freeze for seconds as Rex didn't deliver the final blow as if hesitating. Slowly, he lowered his weapon.
Rex turned his back to it, releasing his spear and letting it dissolve into nothingness. But before he could take a step away, the flame flared up, its tendrils trembling with renewed anger. It seemed as if it refused to accept pity from it's own enemy. But Rex wasn't giving it pity, no it was something else.
Without warning, chains erupted from the ground, forged from Rex's mental power and imagination. They wrapped around the flame, binding it tightly. The entity thrashed and struggled, but it was too drained from the battle to break free.
Rex turned back to face it, his expression resolute. He pointed a finger at the bound flame, his voice ringing with finality.
"You are mine"
"You belong to me now"
"Your power is no longer your own, it is also mine to command"
It would seem that Rex had finally won the battle but it was not the case. Throughout with time, as it recovered it's energy, it tried to break free from the chains again and again, but it wouldn't break. Rex would have to go into his inner world and wait it till the flame clamed down. Slowly with time, its chaotic energy remained, but it no longer lashed out at him.
Subduing the flame didn't mean mastering it outright which he discovered later on. Even after he gained control, the flame refused to obey him willingly. It acted only because Rex's mental power commanded it. In the real world, when using his fire element, he discovered that fact. Every time he summoned it, it consumed some of his mental energy to control it. Where his peers could wield their elements effortlessly, Rex had to strain to maintain control but in return it also helped him as well. Control was something necessary for cultivators to cast spells.
The battles in his inner world had honed his mental power to levels far beyond others his age. Because of this, Rex could wield his flame for longer than others, despite the strain it placed on him.
{End of Flashback}